Recently, web3.0, a network of independent users directly connected to each other, has been attracting attention, and research on digital signature schemes suitable for building systems on web3.0 has been conducted. A ring signature is a type of digital signature that allows one member of a group to anonymously generate a signature on behalf of the group. As an extension of the ring signature, a claimable ring signature that can prove its own signer and a repudiable ring signature that can prove that it is not its own signer are proposed. However, if even one of the keys used to generate the signature is exposed, the signature and the repudiation can be forged. In this study, we propose a ring signature that satisfies that signatures and repudiation are not forged even when the key is exposed. We also describe how to construct an anonymous bulletin board system on web3.0 using the proposed ring signature.